I my self could compared sound quality from mid-2014 MacBookPro11,3 with the high-quality RWAK100 for weeks, using a pair of $400 HD600 (very well-known nicely balanced hp), multiple types of music (classical, jazz, country, rock, pop)
I found almost no different in sound quality with pop, rock or country. Only when listening to some very distinctive records, I counld hear small diffences.
My conclusions:
Sound details: Equal. I didn't miss any small details with my MBP.
Sound feelings: Mostly equal. AK100 had a very small amount of better sound stage in some multi-instrument records (~5%). AK100 sometimes felt a little sweeter to my ears
In my opinion, recent MBP built-in DAC are at high quality, you cannot win it with less than $500 external DAC, AMP. I'm happy with direct sound from MBP for everyday office listening.
Very interesting comparision. If you have a chance, don't miss it